This invention relates to apparatus for manufacturing hollow glass articles such as bulbs for heat-insulated bottles, electric glass bulbs and the like, and, in particular, to work tables used for supporting a charge of molten glass in glass forming machines in such apparatus.
A conventional apparatus for manufacturing hollow glass articles includes a glass feeder and a glass forming machine as shown in, for example, U.S. Pat. No. 2,405,557. The glass feeder is provided with a mechanical shearing device for severing a charge of glass and delivers periodically a charge of glass to the glass forming machine. The glass forming machine includes one or more blowing machines each having a work table, a blowing head and a blowing mold. The work table is formed with an orifice. The delivered charge of glass is received and supported on the work table and depends down through the orifice to form a hollow blank or a parison. The blowing head is brought into contact with the glass blank to enlarge the blank by blowing air into the interior of the parison through the blowing head and, therefore, the parison is blown in the blowing mold to a final shape.
The diameter of the orifice of the work table is determined in dependence on the dimension and shape of the intended hollow glass articles. Therefore, the conventional work table is provided with an orifice plate member having an orifice of a desired diameter and removably mounted thereon, in order to enable the production of hollow glass articles of different shapes and dimensions. Desired glass articles are manufactured by selecting a desired one from various orifice plate members having different diameters and fixing it onto the work table.
The orifice plate member must be removable from the work table to permit the replacement by another orifice plate member having an orifice of different diameter, but it must be fixedly secured to the work table for producing glass articles. To this end, in a conventional work table, the orifice plate is threaded on the outer peripheral surface, and is removably fixed by screwing into the mating screw tapped in the work table. However, the mounting and removal of the threaded orifice plate member is complicated.
In conventional automatic apparatus for manufacturing hollow glass articles, the glass forming apparatus includes a turn table on which a plurality of work tables, for example, 20 or more work tables are mounted. Therefore, it takes a long time to exchange orifice plates for producing different kinds of articles. Furthermore, when a damaged orifice plate is replaced by a new one, the turn table must be stopped for a certain time period sufficient to complete the replacement. This reduces the production efficiency.
Since the work table is in contact with molten glass and subjected to elevated high temperature during the operation, the orifice plate member often becomes attached to the work table. This further makes it difficult to remove the orifice plate member from the work table.